The present invention relates to copper architectural elements and, more particularly, to a simulated patina for such elements.
Patination of copper is a well known process and is desired in many architectural contexts for its unique, blue-green appearance. However, natural patination is very slow, taking as long as 20 years, or more. Thus, while the end result, and even intermediate stages, are considered desirable, the length of the patination process, and the variation in colors during that process, delay the visual effects and complicates any necessary repairs. Indeed, in many instances, the patination of existing copper architectural elements renders their repair aesthetically impractical.
An obvious prior art attempt to mimic patination is the utilization of a uniform coating of paint of a desired tone (color). While this allows the use of cheaper substrates, its effect is not aesthetically pleasing in that paint lacks the unique character and appearance of patinated copper.
A variation of the approach described above is disclosed in U.S. Pat. No. 4,416,940 which discloses a two step process to impart a simulated weathered-copper appearance to a substrate. The first step applies an opaque patina colored base coating to a primed or unprimed substrate. After the base coat is cured, a non-opaque top coat is applied. This second coating contains one or more copper-color-producing additives and has transparencies such that the patina color of the base coat may be perceived through the top coat while the top coat reflects light from its additives to provide a copper color. While this process may better mimic the appearance of patination, it is nonetheless a non-changing coating that does not (on application, or over time) satisfactorily simulate the unique character and aesthetic appeal of patinated copper.
A further attempt to avoid the long patination process is the product available under the trademark EVERGREEN from Revere Copper Products, Inc. This product provides a pre-patinated copper substrate that patinates further following installation. Uniformity in appearance is not available at installation. Further, dependent on the conditions in the region of installation, “maturity” may or may not provide a uniformity of appearance over time. Additionally, and most important, such pre-patinated panels have been known to be harmful to the forming equipment employed in the fabrication of a final panel configuration. That is, pre-patinated materials are typically available in sheets to be bent and/or cut in the desired configuration for installation. The equipment on which these forming operations take place are attacked by the residual materials employed in the pre-patination process such that they require significant additional maintenance and part replacement. This is not only detrimental to the forming equipment but also significantly increases the cost of using the pre-patinated products.